chore: fix trailing comma in package.json (#470)

Author: enzonotario

examples/ecmascript/package.json

@@ -3,7 +3,7 @@
   "version": "2.0.0",
   "description": "Ohm grammars for various editions of ECMAScript (aka JavaScript).",
   "scripts": {
-    "test": "ava",
+    "test": "ava"
   },
   "repository": {
     "type": "git",